#1
math_list <- list(
               array((1:2),dim=c(1,2,3)),
               c(3,9,81),
               matrix(c(9,0,9,0),nrow=2,ncol=2)
)

#2
names(math_list) = c("ThreeDArray", "Vector", "Matrix")

#3
math_list[[4]] = "I did it"

#4
names(math_list[[4]]) = "String"

#5
length(math_list)

#6
math_list[[4]] = NULL

#7
math_vector = math_list[['Vector']]

#8
math_vector = array(math_vector)

#9
new_matrix = math_list[['ThreeDArray']][,,2]

#10
(new_matrix)*math_vector[2]